The present invention relates to an apparatus for manufacturing a semiconductor device.
In conventional semiconductor fabrication techniques, an electrode pad of a semiconductor element (pellet) is connected to an outer lead by looping a gold bonding wire. When a gold wire is used, however, the following problems occur.
(1) When a bonding wire is looped at a high temperature, an intermetallic compound of gold and aluminum is formed at a bonding region between the Al electrode pad and the bonding wire. For this reason, electrical characteristics at the bonding region are degraded.
(2) Even if the gold bonding wire itself is not oxidized, the reliability of the semiconductor device is impaired due to degradation in electrical characteristics at the bonding region.
(3) Since an intermetallic compound of gold and aluminum is formed after the bonding process, a semiconductor device with stable electrical characteristics cannot be manufactured.
(4) Gold wire is expensive and increases the manufacturing cost of the semiconductor device.
In order to resolve the above problems, prospective bonding regions are selectively activated to loop a copper bonding wire between an electrode pad and a copper lead frame, as disclosed in Japanese patent application No. 55-88318. According to this technique, however, a bonding failure occurs due to an oxide formed on the bonding wire. At the same time, it is difficult to form a ball of a predetermined size at a distal end of the bonding wire, thereby resulting in incomplete bonding. In addition, the prospective bonding region must be activated every time bonding is performed, thereby lowering operation efficiency.
In Japanese patent application No. 57-51237, a distal end of a capillary through which a bonding wire extends is introduced into a reducing atmosphere in a cover to form a desired ball. At the same time, oxidation of the bonding wire is prevented, thereby performing bonding. According to this conventional technique, a complicated mechanism including a cover for holding the reducing atmosphere is required. A failure often occurs when a bonding speed is 1 second or less, so that maintenance is cumbersome. In addition, since an oxide on the lead frame having outer leads cannot be eliminated, bonding between the copper bonding wire and the copper lead frame cannot be performed with high reliability.